1. Field of the Invention
The present invention relates to a measurement apparatus, and more particularly to a fiber network events measurement apparatus.
2. Description of Related Art
With reference to FIG. 6, a conventional fiber network testing device, i.e. an FMCW (Frequency-modulated continuous-wave) device comprises a laser emitter 80, an FMCW generator 81, a directional coupler 82, a photo detector 83, a signal converter 84 and a signal control unit 85.
The laser emitter 80 emits a testing beam. The FMCW generator 81 generates a periodic FMCW signal. The testing beam and the FMCW signal are combined and are outputted to a fiber network route 86 through the directional coupler 82. When the FMCW signal is transmitted in the fiber network route 86, the FMCW signal is reflected due to discontinuous planes of fiber cables.
The photo detector 83 receives the reflected energy of the FMCW signal and converts the reflected energy into an electronic signal.
The signal converter 84 is electrically connected to the FMCW generator 81 and the photo detector 83 and has a mixer 841, an amplifier 842, an A/D (analog to digital) converter 843 and a spectrum converter 844. The mixer 841 mixes an original and the reflected FMCW signal to obtain traces as illustrated in FIG. 7. The mixer 841 compares the traces of the two FMCW signals to obtain a comparison result through a frequency difference calculation. The amplifier 842 strengthens the amplitude of the comparison result. The A/D converter 843 converts the comparison result into a digital signal. The spectrum converter 844 acquires a reflection frequency by using fast Fourier transform (FFT) according to the digital signal. The signal control unit 85 then obtains the positions of reflected points A-D as illustrated in FIG. 8.
The positions where the events occur can be effectively determined according to the trace of FIG. 8. However, the signals attenuate when they are transmitting in fiber cables. The attenuation condition of the signals is unobservable in the trace. The information disclosed in the trace is insufficient for determining the state of the fiber network routes.